Drive mechanism for a reciprocating tool

ABSTRACT

Embodiments of the present invention are directed to a drive apparatus for a reciprocating tool, comprising a housing, a rotatable drive shaft assembly located in the housing, an elongated spindle located in the housing for reciprocating motion, a front bushing in the housing for supporting the front end portion of the spindle, and a wobble drive mechanism comprising a wobble drive shaft connected to the drive shaft assembly, an elongated arm having a lengthwise axis extending upwardly from the wobble drive shaft and including an upper interface for reciprocating the spindle generally in its lengthwise direction during alternating cutting and return strokes, wherein the upper interface connects the arm to the spindle in a manner that prevents translational movement of the spindle relative to the arm in the direction of the arm lengthwise axis, but permits rotational movement thereof in three orthogonal axes. 
     Other embodiments of a drive apparatus are disclosed.

BACKGROUND OF THE INVENTION

The present invention generally relates to power hand tools, and moreparticularly, to power reciprocating tools.

Reciprocating tools that are motor driven, such as saber saws, largerreciprocating saws and the like are usually driven by electric motorsthat have a rotating output shaft. The rotating motion is translatedinto reciprocating motion for moving a saw blade or the like in areciprocating manner.

Reciprocating tools such as jigsaws, saber saws, as well as largerreciprocating saws are typically driven by the rotating output shaft ofan electric motor. Such tools have a mechanism that translates rotarymotion of the output shaft into reciprocating motion. Among the types ofmechanisms that convert the rotary motion to reciprocating motionincludes a wobble plate drive mechanism that is well known to those ofordinary skill in the art.

There has been much research and development over the years attemptingto improve the cutting efficiency of such reciprocating saws as well asreduce the vibration that is experienced by users of them. There hasalso been much effort put forth to achieve those goals and also toreduce friction and power consumption with saws that are compact andconvenient to use.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to a drive apparatusfor a reciprocating tool, comprising a housing, a rotatable drive shaftassembly located in the housing, an elongated spindle located in thehousing for reciprocating motion, the spindle having a front end portionfor attaching a cutting blade thereto and a rear portion, a frontbushing in the housing for supporting the front end portion of thespindle, the bushing permitting reciprocating and limited angular motionof the spindle therein, and a wobble drive mechanism comprising a wobbledrive shaft connected to the drive shaft assembly, an elongated armhaving a lengthwise axis extending upwardly from the wobble drive shaftand including an upper interface for reciprocating the spindle generallyin its lengthwise direction during alternating cutting and returnstrokes, wherein the upper interface connects the arm to the spindle ina manner that prevents translational movement of the spindle relative tothe arm in the direction of the arm lengthwise axis, but permitsrotational movement thereof in three orthogonal axes.

Another embodiment is directed to a drive apparatus for a reciprocatingtool, comprising a housing, a rotatable drive shaft assembly located inthe housing, an elongated spindle located in the housing forreciprocating motion in its lengthwise direction, the spindle having afront end portion for attaching a cutting blade thereto and a rearportion, a front bushing in the housing for supporting the front endportion of the spindle, the bushing permitting reciprocating and limitedangular motion of the spindle therein, a wobble drive mechanismcomprising a wobble drive shaft connected to the drive shaft assembly,an elongated arm having a lengthwise axis extending upwardly from thewobble drive shaft and including an upper pivot connection to thespindle for reciprocating the spindle generally in its lengthwisedirection during alternating cutting and return strokes, the upper pivotconnection preventing translational movement of the spindle relative tothe arm in the direction of the arm lengthwise axis, an elongated rockerhaving an upper end portion with an interface to the spindle, a lowerend portion having two spaced apart side walls, each side wall having acounterweight pivot connection for connection to a counterweight, and ahousing pivot connection to the housing located between the upper andlower end portions, a counterweight having a main portion that extendsabove and on opposite sides of the spindle and side portions that extenddownwardly to the counterweight pivot connections, and a supportconfiguration associated with the counterweight and housing forsupporting the counterweight while permitting reciprocating movement ofthe counterweight in the housing in a direction generally parallel tothe spindle movement.

Another embodiment is directed to a drive apparatus for a reciprocatingtool, comprising a housing, a rotatable drive shaft assembly located inthe housing, an elongated spindle located in the housing forreciprocating motion in its lengthwise direction, the spindle having afront end portion for attaching a cutting blade thereto and a rearportion, a front bushing in the housing for supporting the front endportion of the spindle, the bushing permitting reciprocating and limitedangular motion of the spindle therein, a wobble drive mechanismcomprising a wobble drive shaft connected to the drive shaft assembly,an elongated arm having a lengthwise axis extending upwardly from thewobble drive shaft and including an upper pivot connection to thespindle for reciprocating the spindle generally in its lengthwisedirection during alternating cutting and return strokes, the upper pivotconnection preventing translational movement of the spindle relative tothe arm in the direction of the arm lengthwise axis, an elongated rockerhaving an upper end portion with an interface to the spindle, a lowerend portion having two spaced apart side walls, each side wall having acounterweight pivot connection for connection to a counterweight, and ahousing pivot connection to the housing located between the upper andlower end portions, a counterweight having a main portion that extendsabove and on opposite sides of the spindle, side portions that extenddownwardly to the counterweight pivot connections, and a forwardextension from a bottom of each of the side portions, the counterweightpivot connections being connected to the forward extensions, a supportconfiguration associated with the counterweight and housing forsupporting the counterweight while permitting reciprocating movement ofthe counterweight in the housing in a direction generally parallel tothe spindle movement, the support configuration comprising an elongatedslot in each of the side portions oriented in a direction generallyparallel to the spindle movement, and a pin mounted in the housing andoperatively extending to each of the slots and permitting thereciprocating movement, and a cam surface on the wobble drive shaftconfigured to move the pin and the counterweight in a vertical directionduring reciprocation of the counterweight, the opposite ends of the pinbeing mounted in the housing in a manner permitting vertical movementthereof responsive to rotation of the wobble drive shaft and cam forcreating an arcing motion to the counterweight for neutralizing arcingmovement of the spindle.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first preferred embodiment of thepresent invention shown with portions removed to illustrate the drivemechanism of a reciprocating saw;

FIG. 2 is a perspective view similar to FIG. 1, but showing onlyportions of the drive mechanism together with portions of a drivemechanism of a reciprocating saw;

FIG. 3 is a cross section taken generally along the center line of thedrive mechanism shown in FIG. 2;

FIG. 4 is a cross section of the drive mechanism shown in FIG. 2, takenalong a plane defined by the dotted lines in FIG. 2;

FIG. 5 is a perspective view of a second preferred embodiment of thepresent invention, shown with the portions removed to illustrate thedrive mechanism thereof;

FIG. 6 is a side view of a portion of the second preferred embodimentshown in FIG. 5;

FIG. 7 is a cross section taken generally through the center line of thedrive mechanism shown in FIG. 6;

FIG. 8 is a section taken generally along the line 8-8 of FIG. 6;

FIG. 9 is a perspective view showing a portion of a third preferredembodiment of the present invention, illustrating the drive mechanismthereof;

FIG. 10 is a side view of the third preferred embodiment shown in FIG.9;

FIG. 11 is a cross section taken generally along the line 11-11 of FIG.10;

FIG. 12 is a perspective view of a fourth preferred embodiment of thepresent invention, illustrating the drive mechanism thereof;

FIG. 13 is a cross section taken generally along the centerline of thelength of the drive mechanism shown in FIG. 12;

FIG. 14 is a perspective view of a fifth preferred embodiment of thepresent invention shown with portions removed to illustrate the drivemechanism thereof;

FIG. 15 is a cross-section taken along the center line of the drivemechanism shown in FIG. 14, with an orbital control mechanism shown inan ON position and the plunger in its fully retracted position;

FIG. 16 is a cross section taken generally along the line 16-16 of FIG.15, but with the plunger shown in its extended position rather than theretracted position as shown in FIG. 15;

FIG. 17 is a cross section of the fifth preferred embodiment shown inFIG. 16, but illustrating the plunger in its extended position and withthe orbital control mechanism in its OFF position;

FIG. 18 is a cross section similar to FIG. 17, but illustrating theorbital control mechanism in its ON position;

FIG. 19 is a perspective view of a sixth preferred embodiment of thepresent invention shown with portions removed to illustrate the drivemechanism thereof;

FIG. 20 is a side view of the drive mechanism shown in FIG. 19;

FIG. 21 is a cross section taken generally along the line 21-21 in FIG.20;

FIG. 22 is a perspective view of a seventh preferred embodiment of thepresent invention shown with portions removed to illustrate the drivemechanism thereof;

FIG. 23 is a side plan view of the seventh preferred embodiment of thepresent invention shown in FIG. 22;

FIG. 24 is a cross section taken generally along the center line of theembodiment shown in FIG. 23;

FIG. 25 is a cross section taken generally along the line 25-25 of FIG.23;

FIG. 26 is a perspective view of an eighth preferred embodiment of thepresent invention shown with portions removed to illustrate the drivemechanism thereof and illustrating an orbital action control lever in anOFF position;

FIG. 27 is side view of a cross-section taken along the center line ofthe drive mechanism of the reciprocating saw shown in FIG. 26,illustrating the spindle in an extended position and with an orbitalcontrol lever in an ON position;

FIG. 28 is side view of a cross-section taken along the center line ofthe drive mechanism of the reciprocating saw shown in FIG. 26,illustrating the spindle in a retracted position and with an orbitalcontrol lever in an OFF position;

FIG. 29 is a cross section taken generally along the line 29-29 of FIG.28;

FIG. 30 is side view of a cross-section taken along the center line ofthe drive mechanism of the reciprocating saw shown in FIG. 26,illustrating the spindle in a retracted position and with an orbitalcontrol lever in an ON position; and

FIG. 31 is a cross section taken generally along the line 31-31 of FIG.30.

DETAILED DESCRIPTION

Several embodiments of the present invention are described in thepresent specification and shown in the drawings. All embodiments aredirected to reciprocating saw drive mechanisms that employ a wobble armmechanism for reciprocating the spindle of the reciprocating saw, withthe spindle having a clamping mechanism for securing a blade therein.The embodiments all use a wobble plate drive and operate in a mannerwhich is very efficient and utilizes designs which are compact andeffective. While not all embodiments employ a counterweight in theirdesign and construction, many embodiments do and operate in a mannerwhich minimizes the degradation that is created due to the reciprocatingaction of the plunger. Many of the embodiments have components which arecommon to one another and where practical, are given the same referencenumbers. Where components are given the same reference number withregard to different embodiments, it is intended that the function ofthose components would be very similar and may not be described withregard to all of the embodiments. Where structural differences existwith a comparable component, it may be given a prime designation toindicate structural differences.

The preferred embodiments of the present invention are reciprocatingdrive mechanisms for a reciprocating tool such as a reciprocating saw,the general size and shape of which is similar to saws that arecurrently marketed. The present invention is also applicable for othertypes of tools such as saber saws, for example, or other types of toolsthat have a reciprocating action driven by a wobble plate drivemechanism and powered by a motor having a rotating output shaft.

The first embodiment of the present invention is directed to a compactreciprocating saw driven by a wobble plate drive mechanism where thewobble mechanism creates an automatic orbital movement of the bladeduring its reciprocation. The connection between the wobble plate driveshaft to the spindle is a rigid connection in the sense that the spindledoes not move relative to the spindle along the lengthwise direction ofthe wobble arm and therefore causes the spindle to follow in an arcingmotion during reciprocation of the spindle. Stated in other words, asthe wobble drive moves in its reciprocating motion, the motion of theconnection causes the spindle to follow an arcuate path which is similarto an orbital motion. This orbital path is defined by the arcing motionof the wobble arm combined with the location of a front pivoting bushingthat anchors the front portion of the spindle where it exits the frontof the tool. Even though the pivot connection of the end of the wobblearm to the spindle, the spindle is able to rotate in all otherdirections, i.e., except in the lengthwise direction of the wobbleshaft. This movement will be further described in connection with thedrawings, and particularly FIGS. 1-4.

Referring to FIGS. 1-4, a reciprocating saw, indicated generally at 10,has a housing 12 which includes a nose portion indicated generally at 14that is flared outwardly so that a user can hold the nose portion withone hand while holding a handle, indicated generally at 16, with theother. A trigger switch 18 is provided in the handle portion 16 forturning on a motor 20 that drives the tool. The saw has a shoe 22 at thenose end portion 14 and a saw blade 24 is mounted in a blade clampingmechanism 26 that is mounted at the end of an elongated spindle,indicated generally at 28. The motor 20 has an output shaft 34 with apinion gear 36 and fan member 38 operatively attached to the shaft 34,with the gear 36 engaging a larger gear 40 that is connected to a wobbledrive mechanism, indicated generally at 42, which drives the spindle 28in a reciprocating manner. The teeth of the pinion gear 36 and gear 40are not shown for the sake of simplicity, but are conventional as isknown to those of ordinary skill in the art.

More particularly, the wobble drive mechanism 42 has a drive shaft 46 towhich the gear 40 is attached. The shaft has an end portion that issupported in a needle bearing 50 or the like and an opposite endsupported in another ball bearing 54 that is mounted in the housing 12.It should be understood that the manner in which the motor 20, gears 36and 40 as well as the shaft 46 are mounted in the housing 12 is notshown in detail inasmuch as such is conventional and is also well knownto those of ordinary skill in the art.

With regard to the wobble drive mechanism 42, the shaft 46 has generallycylindrical shaped portion 60 best shown in FIG. 3 that is oriented atan acute angle θ relative to the axis of the shaft 46 as shown by adashed line 62. The wobble drive mechanism 42 has an elongated arm,indicated generally at 64, that is mounted in ball bearings 66 forrotation relative to the cylindrical portion 60, which permits the arm64 to move in a left and right direction relative to the cylindricalportion 60 as the shaft 46 is rotated during operation.

More particularly, as the shaft 46 is rotated, the angular orientationof the cylindrical portion 60 changes, and the arm 64 of the wobbledrive mechanism 42 is moved in a reciprocating manner, i.e., to the leftas shown in FIG. 2, and to the right as shown in FIG. 3. Such operationis well known to those of ordinary skill in the art.

As is shown in all of the FIGS. 1-4, the elongated arm 64 is made of abase arm portion 68 which has a cylindrical aperture 70, its upper end72 that extends a substantial distance to a level adjacent the ballbearings 66. The aperture 70 is sized to receive an arm adaptor 74 whichis snuggly fit in the aperture but which is capable of rotating movementaround a center axis identified by line 76 of FIG. 3. The adaptor 74 isconnected to the base arm portion 68 by a pin 78 that fits within asuitable aperture 80 in the adaptor 82 which is sized so that the pin 78can rotate a limited degree around the center line 76. The pin 78 ispreferably centered in the width of the slot 82 so that it can rotate ineither direction around the axis 76 of the adaptor 74. The rotatabilityof the adaptor in the base arm portion 64 enables stresses to be removedthat are generated by reciprocating motion of the spindle 28.

The rigid connection of the elongated arm 64 to the spindle 28 isprovided by a pin 86 that extends through the upper end portion of theadaptor 74 and suitable apertures in the right end portion, indicatedgenerally at 84 of the spindle 28. The side end portion 84 has aslightly enlarged diameter portion as well as recesses 88 in the top andbottom thereof which enable the adaptor to be inserted therein and thepin 84 enables pivoting movement between the spindle 28 and the adaptor74. It should be understood that the reciprocating motion of the wobbledrive mechanism 42 results in rotation of the elongated arm 64 relativeto the dashes? 62 of the shaft 46 and for that reason, it must belimited which in the present embodiment is provided by a pair ofcylindrical rods 90 that are shown in the drawings, with one of the rodsbeing provided on each side of the space arm portion 68, suitablymounted in the housing to prevent such rotational movement of theelongated arm 64. In this regard, and as best shown in FIGS. 1, 2 and 4,the cylindrical rod 90 contacts a curved surface of the base arm portion68 in a generally perpendicular orientation which results in a singlepoint contact between each rod and the base arm portion 68 whichminimizes friction.

During rotation of the shaft 46, the wobble drive mechanism 42 effectivepivots around the center of the cylindrical portion 60, identified atpoint 92, so that the rigid pivot pin 86 will travel through an arc andapplied by the dotted line 94 has the wobble drive mechanism move thespindle. Since the pivot pin 86 is centered in the spindle as shown inFIG. 3, the spindle will move vertically during its reciprocating travelso that the pin 86 will traverse the path identified by the line 94. Thespindle is slidable in a bushing 96 located at the nose portion 14 ofthe housing 12 and it has a spherical outer surface 98 that is suitablymounted in a similar curved surface so that the angle of the spindle canchange.

As should be appreciated by considering FIG. 3, the blade which is leftof the front bushing 96 will move downwardly as the right end portionbefore elevated during the reciprocating motion. It should be understoodthat the cutting action is generally on a return to its fully retractedposition which is shown in FIG. 3 so that as the blade is moved to theright cutting through the work piece or the like, the rear end 84 ismoving upwardly which causes the blade to move more aggressively intothe work piece which is a desirable feature and the subject of suchorbital action. It should be understood that while changing the angle ofthe blade during engagement with a work piece is commonly referred to asorbital action which provides a more aggressive cutting action duringthe return or cutting scope, it should be understood that suchcharacterization may not be entirely orbital but in a nonlinear mannerwhich achieves the same goals. The spherical surface 98 of the frontbushing 96 allows it to rotate freely in all three axes because of thespherical connection between the housing and the bushing.

A second preferred embodiment is shown in FIGS. 5-8 which have manyfeatures that are similar to the embodiment shown in FIGS. 1-4. Aprincipal difference in the second preferred embodiment is the additionof a counterweight which counterbalances the reciprocating saw mechanismand provides for left vibration and a smoother feeling operation by auser. The counterweight is efficiently incorporated into the design sothat it is compact and is nearly the same size as the FIG. 1configuration. The design utilizes the rigid pivot connection betweenthe spindle and the wobble drive mechanism to thereby achieve the sameorbital or nonlinear type of cutting motion during reciprocation of theblade.

Referring to FIGS. 5-8, the embodiment, indicated generally at 100,includes a counterweight, indicated generally at 102, which ispreferably made of steel and has sufficient mass to balance the forcesgenerated by the plunger and its drive mechanism. The counterweight 102is designed and configured to surround the spindle 28 so that it has acenter of gravity that approximates the center of gravity of the spindleduring operation. Such configuration results in less vibration. To thisend, the counterweight 102 has a top portion 104 that merges with sideportions 106. The side portions 106 extend downwardly to slightlyoutwardly flared transition portions 108 that merge with lower legportions 110. As is best shown in FIGS. 7 and 8, the thickness of the

As is shown in FIG. 5, the drop side portions 106 and transitionportions 108 have a cutout portion 112 removed. This is done for thepurpose of proper weight distribution and such cutout portions 112 mayor may not be provided depending upon the necessary mass that isrequired for achieving the desired counterbalancing. The lower legportions 110 also have a forward extension 114 with a pivot connector116 that is connected to a rocker arm, indicated generally at 120, thatis also connected to the spindle 28 and operates to reciprocate thecounterweight 102 in a direction opposite that of the movement of thespindle 28.

The rocker arm 120 has a pivot pin 122 that rides in bearings (notshown) and the rocker arm 120 pivots about the pin 122 during operation.The rocker arm 120 has an upper arm portion 124 which terminates in aspherical ball end portion 126 that rides in a cylindrical aperture 128which is located in a thickened top portion 130 of the spindle 28. Theupper arm portion 124 extends through a suitable opening 132 in thebottom of the plunger during reciprocation of the spindle 28, because ofthe rigid connection 86 between the wobble drive mechanism 64 and thespindle 28, the spindle will move in a vertical manner duringreciprocation of the spindle and therefore there will be some relativemovement between the ball 126 and the cylindrical opening 128 duringoperation. Additionally, there will be pivoting movement so that theball will not only pivot, but will also slide within the cylindricalopening 128. The rocker arm 120 also has a lower extension 134 thatconnects to the forward extension 114 of the counterweight 102. This isachieved by the pivot connection 116. The relative distance between thepivot connection 122 and the ball 126 compared to the distance betweenthe pivot connection 122 and 116 will determine the amount of movementthat the counterweight travels during a cutting and return stroke of thespindle 28. Such distances can be changed depending upon the mass of thecounterweight, the dynamics of the wobble drive mechanism and spindleand such consideration can be optimized to achieve the desired reductionin vibration. Such analysis is known to those of ordinary skill in theart of tool design.

The counterweight 102 is mounted in the housing and is supported by apair of generally horizontally oriented bushings 136 which arepreferably pressed into the housing but is not shown in the drawings.The bushings 136 have a recess defined by a bottom surface 138 andopposed inclined surfaces 140. The recesses extend at least the lengthof travel that is provided for the counterweight 102 and the recessescooperate with an associated rolling ball 142 which is sized to contactthe inclined surfaces 140 and not the bottom surface 138. The balls 142also contact a complimentary pair of inclined surfaces 144 in the lowerright portion 110, with these surfaces 144 terminating in an opening 146that extends through the entire thickness of the lower length 110. Thisconnection enables the counterweight to be moved along a desired pathrelative to the housing and be supported in a manner that is extremelyefficient. In this regard, the bushings 136 are shown to have a recessthat is straight and oriented substantially horizontally. However, itshould be understood that it may be oriented at an angle to change thevertical position of the counterweight during its reciprocation.Further, it may be curved along its length to provide a desired profileof vertical movement during such reciprocation to balance the movementof the spindle, or stated in other words, to optimize the reduction ofvibration created by the spindle by the counterweight movement duringoperation.

The connection utilizes the two rolling balls 142 that are captured bythe bushings 136 that are pressed into the front housing. The balls 142are captured by the two chamfered surfaces 140 in the bushings 136 whichare preferably oriented less than 45° relative to the bottom surface 138to allow the balls 142 to rotate freely in all directions and contactthe bushing with single edge contacts at two points. The counterweight102 also has two V-groove inclined surfaces 144 that are also less than45° from the contact plane which allows the rolling balls to roll in thegrooves as the counterweight moves back and forth. The connection allowsfor rotation of the counterweight in all directions and is an efficientway for the counterweight to move back and forth, in reducing friction.As is evident, the contact system also constrains the counterweight frommoving in a side to side direction.

A third preferred embodiment is shown in FIGS. 9-11 which is verysimilar to the second preferred embodiment shown in FIGS. 6-8. Becausemost of the components of the embodiment shown in FIGS. 9-11 areidentical to those shown in the second preferred embodiment shown inFIGS. 6-8, the reference numbers are not applied to a vast majority ofthe components shown in FIGS. 9-11. However, the differences arediscussed and generally relate to the support of the counterweight 102′.More particularly, the counterweight 102 has a pair of horizontallyoriented elongated slots 150 located in the lower leg 110 of thecounterweight 102′, with the length of the horizontal slots 150generally corresponding to the length of travel of the counterweight102′ produced by the wobble drive mechanism 42. The counterweight 102′has a horizontal shaft 152 that extends between both sides 110 and isjournaled in needle bearings 154 that have their outer braces mounted ina suitable recess within the housing 12 (not shown). The needle bearingsenable the shaft 152 to rotate within the needle bearings 154 so thatduring reciprocating motion by the counterweight 102′, the shaft 152 isfree to rotate within the slots 150.

It should be understood that the width of the slots 150 should beapproximately equal to the diameter of the shaft 152 at the locationwhere the shaft is coextensive with the leg portions 110 and as shown inFIG. 11, the shaft 152 has a slight spherical shaped bulge where itcontacts the counterweight 102′ for the purpose of providing generallypoint to point contact between the shaft 152 and the upper surface ofthe slot 150 for the purpose of reducing friction during movement of thecounterweight.

A fourth preferred embodiment of the present invention is shown in FIGS.12 and 13 and all of the components thereof have not been provided,because these embodiments have components that are common with theembodiments of FIGS. 1-4 as well as FIGS. 9-11. The embodiment shown inFIGS. 12 and 13 has a rocker arm 120′, which is similar to the rockerarm 120 shown in the embodiment of FIGS. 9-11, but with differences thatwill be hereinafter described. Similarly, a counterweight 102″ isprovided with differences between that and the counterweights 102 and102′ being identified. A significant difference in the embodiment ofFIGS. 12 and 13 is that the counterweight 102″ is supported andreciprocates in a pair of slots 160 which are suitably secured in thehousing 12 (not shown) and have a length that is sufficient to permitthe counterweight 102″ to reciprocate through its full return andcutting strokes. The outside diameter of the rods 160 is sized slightlysmaller than the inside diameter of a bushing 162 that is mounted in anenlarged portion of a top side portion 106′ of the counterweight 102″.

As is evident from FIG. 12, the lower leg portion 110′ does not have thehorizontal slots that are present in the embodiment of FIGS. 9-11 orwell as that shown in FIGS. 5-8. Since the counterweight does not pivotas it is reciprocated by the inner connection with the rocker arm 120′,the interconnection of the forward extension 114′ is designed to enablevertical movement of the pivot connection to accommodate the verticalmovement of the rocker arm during the reciprocating action. In thisregard, the forward extension 114′ has an elongated slot 164 that isoriented in a vertical direction and the lower part of the rocker arm120′ has a fixed pin 166 sized approximately slightly smaller than thewidth of the slot 164 so that the pin can ride up and down in the slotduring pivoting action of the rocker arm around its pivot pin 122. Theinterconnection of the upper end of the rocker arm 120 with the spindle28′ is slightly different than that shown in the embodiment of FIGS. 5-8which employ the ball end 126 that rides in a cylindrical opening 128 abest shown in FIG. 7.

In the embodiment of FIGS. 12 and 13, an enlarged portion 168 of thespindle 28′ has a vertical slot 170 that extends through both sidewallsof the spindle 28′ and the upper portion 124′ has a pin 172 that extendsbetween the spaced arm portion 124′. Because the wobble drive mechanism42 has a fixed connection between it and the spindle 28′, it will bealternately raised and lower to follow the path as described with regardto the embodiment shown in FIGS. 1-4 and particularly as described withregard to the arc 94 shown on FIG. 3. The movement of the spindle 28′ inthe vertical direction during reciprocation of the spindle

A fifth preferred embodiment is shown in FIGS. 14-18 which has featuresthat are common with several other embodiments and which will be broadlydescribed hereinafter. The reference numbers for detailed items ofcommon features are omitted where the structure and functionality issubstantially similar to those of other preferred embodiments. If thatis not the case, then the reference number for such structure will beidentified.

The fifth preferred embodiment shown in FIGS. 14-18 has a counterweight102 substantially similar to that shown in the second preferredembodiment of FIGS. 5-8, with slight modification that will behereinafter described. The counterweight 102 is driven by a forwardrocker arm 120 that is also substantially similar to that shown in theFIGS. 5-8 in that it has a spherical ball structure 126 at the upper endof the rocker arm 120 that rides in a cylindrical opening 128 of thespindle 28″.

This embodiment has an orbital or nonlinear movement similar to themovement shown in the embodiment of FIGS. 1-5, but has the addedcapability of being turned on and off by an orbital on and off levermechanism 180 which comprises an elongated rod 182 that has a flatportion 184 which selectively engages a pivotable retaining bushing,indicated generally at 190, for selectively enabling and disablingpivoting movement of the bushing 190 during reciprocation of the spindle28″. The lever mechanism 180 has a handle 192 that an operator canrotate to turn the orbital action on and off as desired. The retainingbushing 190 has a right end portion 194 as shown in the drawings whichis pivotally connected by a pivot pin 196 that is suitably secured inthe housing 12 (not shown). The bushing 190 has a relatively largecylindrical opening 198 configured to retain an enlarged spherical endportion 200 on the spindle 28″.

The length of the cylindrical opening 198 is sufficient to enable thespindle to ride through its full cutting and return strokes. The lowerwall of the retaining bushing has a cut-out region, indicated generallyat 202, that permits the wobble drive mechanism 42′ to guide the spindle28″ through its complete strokes. As is shown in FIGS. 17 and 18, thespindle is fully extended and in FIG. 15, it is shown substantiallyfully retracted where the spherical end portion 202 is near the rightend of the cylindrical opening 198.

The orbital action of the blade is achieved by the spindle 28″. Thevertical movement of the spherical end portion 200 is achieved bypivoting the retaining bushing 190 about its pivot pin 196. The pivotingaction is achieved by the interaction of a cam member 204 engaging adownward extension 206 of the retaining bushing 190. The cam is designedto provide the desired vertical change of the spherical end portion 200during the cutting and return strokes of the spindle 28″ duringreciprocation. Such desired motion is a function of the shape of the camand that is within the level of ordinary skill of those in themechanical design arts.

Since the orbital movement of the spindle 28″ is achieved by the actionof the cam member 204 on the retaining bushing 190, the wobble drivemechanism 42 is modified compared to the wobble drive mechanism 42 shownin FIGS. 1-4 and particularly FIG. 3. The modification involves theelimination of a pin 78 which prohibits the adaptor 74 from axialmovement in the direction of the line 76 relative to the base armportion 68. Thus, in the configuration shown in FIGS. 14-18, the adaptor74 is connected to the spindle 28″ by the pin 86 and is a rigid pivotalconnection which results in the adaptor 74 moving relative to the basearm 68.

When the orbital on and off lever mechanism 180 is positioned as shownin FIG. 17, the retaining bushing is prohibited from pivoting thedownward direction as is apparent by the gap between the end of thedownward extension 206 and the adjacent outer surface of the cam member204. When the orbital lever mechanism 180 is placed in its on position,as shown in FIG. 18, the retaining bushing 190 is shown to have beenpivoted to a lower position by the cam member 204. The counterweight 102is supported by bushings 136 that operate in the same manner asdescribed with regard to the embodiment shown in FIGS. 5-8.

A sixth preferred embodiment is shown in FIGS. 19-22 which has manycomponents that are substantially similar to other embodimentspreviously described including a counterweight 102 which is driven by arocker arm 120 that is substantially similar to that shown and describedwith regard to the embodiment of FIGS. 14-18 and has a wobble drivemechanism 42 that is substantially similar to that shown in FIGS. 1-4,which includes the elongated arm 64 as is also shown and described inthose figures. The spindle is driven through the nonlinear arc asdescribed with regard to the embodiment of FIGS. 1-4, however, the sixthpreferred embodiment has the counterweight 102 modified in a mannerwhereby the counterweight is mounted and driven in a manner whereby thecounterweight 102 itself is moved vertically as it is reciprocated backand forth. The movement is done in a manner whereby the counterweightmotion is synchronized to optimize its position to match that of theplunger shaft orbital movement.

This movement effectively reduces the vibration of the mechanism in thevertical direction. This is achieved by providing a horizontal shaft152′ that fits within horizontal slots 150 on each lower leg portion 110which shaft 152′ is similar to that shown and described with regard toshaft 150 in the configuration shown in FIGS. 9-11, except that theshaft has a slightly reduced size annular groove 210 located on oppositesides of each leg in which C clips 212 are mounted for the purpose ofmaintaining the shaft 152 centered relative to the counterweight. Theouter ends of the shaft 152′ are secured in elongated bushings 212 thathave a vertical bushing 214 that has a width slighter larger than theoutside diameter of the outer end portions of the shaft 152′ so that theshaft can move vertically within the bushing 214. Slots 216 are providedin the bushing 214 and include a spring 218 to bias the rod 152′downwardly so that the center of the shaft is maintained in contact witha cam member 220 that is mounted on the drive shaft 46. The bushing 214is suitably mounted in the housing 12 (not shown). As previouslymentioned, the configuration of the cam member surface 220 can besynchronized so that the shaft 152′ and counterweight 102 will bevertically moved during reciprocation of the spindle 28″ andcounterweight 102 to optimize the counterweight position during suchreciprocation so that the motions of the two components are matched toreduce the vibration of the mechanism in the vertical direction.

A seventh preferred embodiment is shown in FIGS. 22-25 which is verysimilar to the configuration shown in FIGS. 20-22 with regard to thewobble drive mechanism 42, the rocker arm 120, the spindle 28″ and thecounterweight 102, with the latter being supported by a modifiedmechanism. The modifications relate to the horizontal shaft 152″ whichhas the same interface with the lower legs 110 of the counterweight 102,but the outer ends do not extend significantly beyond the outsidesurface of the legs 110 which therefore contributes to the compactnessof the design. The horizontal shaft 152 is secured in a cylindricalopening 222 of a link member 224 that extends downwardly below thebottom surface of the counterweight 102 and which is mounted invertically oriented bushings 226 in which balls 228 are provided whichride in a vertical channels 230 provided in the link member 224. Thelink member has a horizontal slot 232 with a vertical dimension that isslighter larger than the outside diameter of the cam member 234 which ismachined in the drive shaft 46. The cam member causes the link member224 to move vertically relative to the bushings 226 which are suitablymounted in the housing 12 (not shown). The horizontal shaft 152 isalternatively fixed in the link member 224 so that it does not rotate orit may be rotatable within the cylindrical opening 222 or it may besecured in suitable bearings to rotate freely than if it has contactthroughout its length within the link member 224. As is the case for theembodiment shown in FIGS. 19-21, the cam surface may be designed so thatthe counterweight 102 will be vertically moved during its reciprocationin order to balance against the movement of the spindle and the wobbledrive mechanism 42 to minimize the vibration that it is produced duringoperation of the reciprocating saw.

An eighth preferred embodiment is shown in FIGS. 26-31 and is broadlysimilar to the embodiment particularly shown in FIGS. 14-18 and also hasfeatures that are common with several other embodiments. The referencenumbers for detailed items of common features may be omitted where thestructure and functionality is substantially similar to those of otherpreferred embodiments and have been described with regard to thoseembodiments. If a feature is slightly different from that previouslydescribed with regard to the embodiment shown in FIGS. 14-18, it may begiven a slightly different designator to note its differences.

The eighth preferred embodiment shown in FIGS. 26-31 has a counterweight102 substantially similar to that shown in the preferred embodiment ofFIGS. 14-18. counterweight 102 is driven by a forward rocker arm 120that is also substantially similar to that shown in the FIGS. 5-8 inthat it has a spherical ball structure 126 at the upper end of therocker arm 120 that rides in a cylindrical opening 128 of the spindle28″.

This embodiment has a nonlinear movement capability of that can beturned on and off by an orbital ON and OFF lever mechanism 180′ whichcomprises an elongated rod 182′ that has an oval or ellipticalcross-sectional cam surface configuration, i.e., it has a major axis anda minor axis, which cam surface engages the outer lower surface of aretaining bushing, indicated generally at 190, that pivots around apivot pin 191 for selectively positioning the angle of the center axisof the bushing 190 relative to the pivot pin 191 during reciprocation ofthe spindle 28″. The lever mechanism 180′ has a handle 192 that anoperator can rotate to control the angle of the retaining bushing andtherefore non-linear blade movement action as desired.

In this regard, and referring to FIG. 28, the rear spherical end portion200 rides within the cylindrical chamber 198 of the retaining bushing190 which is shown in its retracted position in FIGS. 28 and 30 and in aforwardly extended position as shown in FIG. 27. It should be understoodthat as the spindle 28″ reciprocates by being driven by the elongatedarm 64, the spherical end portion 200 will also be selectively moved ina vertical direction during such reciprocation as a function of theangular position of the retaining bushing 190 relative to the pivot pin191.

If the center axis of the cylindrical chamber 198 (and therefore thecenter axis of the bushing 190 itself) is perfectly horizontal, thespindle 28′ will be moved in a perfectly horizontal manner and in thathorizontal position, there is no nonlinear, i.e., vertical motionimparted to a blade that is attached to the free end of the spindle 28″.Such a horizontal position is shown in FIGS. 26 and 28, wherein thehandle 192 is in a vertical orientation and the elongated rod camsurface 182′ has its major axis oriented vertically so that it urges theretaining bushing 190 to a nearly true or substantially horizontalposition. However, when the handle 192 is rotated 90° to a relativelyhorizontal position, such as shown for the lever 180 in the embodimentshown in FIG. 14, the axis of the retaining bushing 190 will be angleddownwardly in the forward direction as shown in FIGS. 27 and 30.

When the retaining bushing 190 is positioned so that it is angleddownwardly as shown in FIGS. 27 and 30, the spherical end portion 200will move downwardly as the spindle 28″ is moved to its leftward orextended position which will cause the blade to move upwardly becausethe spindle 28″ is constrained by the bushing 96 that is located betweenthe blade and the end portion 200. As the spherical end portion movesfrom its fully extended position rightwardly toward the fully retractedposition, the blade will be moved downwardly as the spherical endportion 200 is moved upwardly during its travel.

Such change in the elevation of the blade will create a more aggressiveengagement of the saw blade with a work piece which can acceleratecutting depending upon the type of material that is being cut. It shouldbe understood that such nonlinear action results in a curved path ofmovement by the blade, but the blade follows an identical line duringcutting stroke as well as the return stroke, which is not a true orbitalpath which is traversed by a blade in accordance with most prior artcircular saw designs.

It should also be understood that the amount of movement by the camsurface 182′ may only cause a change in elevation of the outer surfaceof the cam 182′ on the outer surface of the retaining bushing 190 by asmall distance, such as a single millimeter. In this regard, the actualshape of the elongated rod cam surface 182′ is exaggerated in FIGS. 27,28 and 30. While it should be evident from the description of theembodiment of FIGS. 14-18, the spherical end portion 200 of the spindle28″ is able to travel within the cylindrical chamber 198 withoutinterference, because the arm adapter 74 is axially adjustable withinthe base arm portion 68 of the elongated arm 64 which drives the spindle28″.

While various embodiments of the present invention have been shown anddescribed, it should be understood that other modifications,substitutions and alternatives are apparent to one of ordinary skill inthe art. Such modifications, substitutions and alternatives can be madewithout departing from the spirit and scope of the invention.

Various features of the invention are set forth in the following claims.

1. A drive apparatus for a reciprocating tool, comprising; a housing; arotatable drive shaft assembly located in said housing; an elongatedspindle located in said housing for reciprocating motion, said spindlehaving a front end portion for attaching a cutting blade thereto and arear portion; a front bushing in said housing for supporting the frontend portion of said spindle, said bushing permitting reciprocating andlimited angular motion of said spindle therein; and a wobble drivemechanism comprising a wobble drive shaft connected to said drive shaftassembly, an elongated arm having a lengthwise axis extending upwardlyfrom said wobble drive shaft and including an upper interface forreciprocating said spindle generally in its lengthwise direction duringalternating cutting and return strokes; wherein said upper interfaceconnects said arm to said spindle in a manner that preventstranslational movement of said spindle relative to said arm in thedirection of the arm lengthwise axis and therefore causes a cuttingblade attached to said front end portion to travel through an arc-likepath that is traversed in said cutting and return strokes.
 2. A driveapparatus as defined in claim 1 wherein said upper interface permitsrotational movement thereof in three orthogonal axes.
 3. A driveapparatus as defined in claim 1 wherein said upper interface comprisesan adapter that is configured to be connected to said arm and saidspindle by first and second pivot connections at opposite end portions,said pivot connections being oriented perpendicular to one another, saidfirst connection between said adapter and said arm permitting side toside pivoting movement of said spindle, and said second connectionbetween said adapter and said spindle permitting reciprocating movementof said spindle in its lengthwise direction.
 4. A drive apparatus asdefined in claim 3 wherein said arm has an upper end portion with arecess configured to receive said adapter, said adapter having agenerally cylindrical shape with a lengthwise axis and being sized toloosely fit within said recess and be pivotable in two orthogonaldirections relative to said arm.
 5. A drive apparatus as defined inclaim 4 wherein said first pivot connection comprises a first pininterconnecting said adapter and said arm, said first pin being orientedgenerally in the lengthwise direction of said spindle to thereby permitsaid side to side pivoting movement of said spindle.
 6. A driveapparatus as defined in claim 5 wherein said second pivot connectioncomprises a second pin interconnecting said adapter and said spindle,said second pin being oriented perpendicular to the lengthwise axis ofsaid adapter and perpendicular to said first pin.
 7. A drive apparatusas defined in claim 6 wherein said arm has at least one elongated slotin which said first pin is positioned, said slot permitting rotation ofsaid adapter about its lengthwise axis through a predetermined angulararc in said arm, while prohibiting movement of said adapter in said armin the direction of said arm axis.
 8. A drive apparatus as defined inclaim 1 further comprising structure operatively associated with saidhousing on opposite sides of said arm for limiting angular movementthereof relative to said lower pivot connection to said drive shaftassembly.
 9. A drive apparatus as defined in claim 8 wherein saidstructure comprises a pair of elongated rods secured in said housing onopposite sides of said arm positioned to maintain said arm in a verticalposition during reciprocation of said spindle.
 10. A drive apparatus fora reciprocating tool, comprising; a housing; a rotatable drive shaftassembly located in said housing; an elongated spindle having alengthwise axis located in said housing for reciprocating motion, saidspindle having a front end portion for attaching a cutting blade theretoand a rear portion with an outwardly curved outer surface; a frontbushing in said housing for supporting the front end portion of saidspindle; a wobble drive mechanism comprising a wobble drive shaftconnected to said drive shaft assembly, an elongated arm having alengthwise axis extending upwardly from said wobble drive shaft andincluding an upper interface for reciprocating said spindle generally inits lengthwise direction during alternating cutting and return strokes,said upper interface connecting said arm to said spindle in a mannerthat permits translational movement of said spindle relative to said armin the direction of the arm lengthwise axis; and a back bushingoperatively connected to said housing and comprising a cylindricalchamber configured to receive said outwardly curved outer surface ofsaid rear portion of said spindle in close sliding engagement, the rearend portion of said back bushing being pivotably connected to saidhousing to permit pivoting movement of said bushing thereby providingorbital movement of said spindle during reciprocating motion thereof; acam mechanism operatively associated with said drive shaft assemblyconfigured to pivot said back bushing during reciprocating motion ofsaid spindle; an on/off lever mechanism for selectively permittingpivoting movement of said back bushing when placed in an on position andpreventing pivoting movement of said bushing when placed in an offposition.
 11. A drive apparatus as defined in claim 10 wherein saidpivot connection is comprised of a shaft operatively anchored in saidhousing oriented transversely relative to said spindle lengthwise axispermitting said back bushing to pivot in a vertical direction.
 12. Adrive apparatus as defined in claim 10 further comprising an elongatedrocker having an upper end portion with an interface to a mid portion ofsaid spindle, a lower end portion with at least one pivot connection forconnection to a counterweight, and a pivot connection to said housingbetween said upper and lower end portions.
 13. A drive apparatus asdefined in claim 10 wherein said front bushing permits reciprocating andlimited angular motion of said spindle therein.
 14. A drive apparatus asdefined in claim 12 wherein said lower end portion of said rocker hastwo spaced apart portions, each of which have a pivot connection forconnection to a counterweight, said apparatus further comprising acounterweight having a main portion that extends above and on oppositesides of said spindle and side extensions that extend downwardly to saidpivot connections, said counterweight being mounted for reciprocatingmovement in said housing.
 15. A drive apparatus for a reciprocatingtool, comprising; a housing; a rotatable drive shaft assembly located insaid housing; an elongated spindle located in said housing forreciprocating motion in its lengthwise direction, said spindle having afront end portion for attaching a cutting blade thereto and a rearportion; a front bushing in said housing for supporting the front endportion of said spindle, said bushing permitting reciprocating andlimited angular motion of said spindle therein; and a wobble drivemechanism comprising a wobble drive shaft connected to said drive shaftassembly, an elongated arm having a lengthwise axis extending upwardlyfrom said wobble drive shaft and including an upper pivot connection tosaid spindle for reciprocating said spindle generally in its lengthwisedirection during alternating cutting and return strokes, said upperpivot connection preventing translational movement of said spindlerelative to said arm in the direction of said arm lengthwise axis; anelongated rocker having an upper end portion with an interface to saidspindle, a lower end portion having two spaced apart side walls, eachside wall having a counterweight pivot connection for connection to acounterweight, and a housing pivot connection to said housing locatedbetween said upper and lower end portions; and a counterweight having amain portion that extends above and on opposite sides of said spindleand side portions that extend downwardly to said counterweight pivotconnections; a support configuration associated with said counterweightand housing for supporting said counterweight while permittingreciprocating movement of said counterweight in said housing.
 16. Adrive apparatus as defined in claim 15 wherein said counterweight has anend view generally in the shape of an inverted U.
 17. A drive apparatusas defined in claim 15 wherein said counterweight has a forwardextension from the bottom of each of said side portions, saidcounterweight pivot connections being connected to said forwardextensions, thereby creating an arcing motion to said counterweight forneutralizing arcing movement of said spindle.
 18. A drive apparatus asdefined in claim 15 wherein said support configuration comprises anelongated recess in each of said side portions, said recess having alength and configuration for providing a desired profile of movementduring reciprocation of said counterweight, and a pin mounted in saidhousing and operatively extending to each of said slots and permittingsaid reciprocating movement.
 19. A drive apparatus as defined in claim18 wherein said pin is a single elongated cylindrical pin havingopposite ends mounted in said housing and extends from between saidrecesses of said side portions.
 20. A drive apparatus as defined inclaim 19 wherein said cylindrical pin is rotatable about its cylindricalaxis relative to said housing.
 21. A drive apparatus as defined in claim19 wherein said cylindrical pin has at least one end fixed to saidhousing and said support configuration further comprises a needlebearing with an inner race and an outer race located in each of saidrecesses, said inner race being mounted on said pin and said outer racebeing sized to move in its associated recess.
 22. A drive apparatus asdefined in claim 15 wherein said support configuration comprises av-shaped groove having side surfaces in each of said side extensionsoriented in a direction generally parallel to said spindle movement, anda bushing mounted in said housing, said bushing having a rotatable balloperatively extending to each of said grooves permitting saidreciprocating movement.
 23. A drive apparatus as defined in claim 22wherein said grooves have side surfaces that are less than approximately45 degrees relative to one another so that each of said balls contactboth of said side surfaces in a point to point contact manner.
 24. Adrive apparatus as defined in claim 19 further comprising a cam surfaceon said wobble drive shaft configured to move said pin and saidcounterweight in a vertical direction during reciprocation of saidcounterweight, said opposite ends of said pin being mounted in saidhousing in a manner permitting vertical movement thereof responsive torotation of said wobble drive shaft and cam.
 25. A drive apparatus asdefined in claim 24 wherein said cam surface is provided on a cam membermounted on said wobble drive shaft.
 26. A drive apparatus as defined inclaim 24 further comprising at least two bushings operatively connectedto said opposite ends of said pin, each of said bushings being mountedin a vertical recess in said housing and permitting vertical movement ofsaid pin.
 27. A drive apparatus as defined in claim 26 furthercomprising a member for biasing said pin toward said cam.
 28. A driveapparatus as defined in claim 27 wherein said member is a compressionspring.
 29. A drive apparatus as defined in claim 15 wherein saidsupport configuration comprises an elongated recess in each of said sideportions oriented in a direction generally parallel to said spindlemovement, and an elongated cylindrical pin located in said recesses andextending between said recesses of said side portions, said apparatusfurther comprising a cam surface on said wobble drive shaft and a camlink attached to said pin having a cam follower surface engaging saidcam surface to positively move said pin, cam link and counterweight in avertical direction during reciprocation of said counterweight.
 30. Adrive apparatus as defined in claim 29 further comprising bushingsoperatively connected to said housing located on opposite sides of saidcam link to prevent sideways movement of said cam link relative to saidhousing while permitting vertical movement thereof.
 31. A driveapparatus as defined in claim 30 wherein said bushing have rotatableball for contacting said cam link.
 32. A drive apparatus as defined inclaim 29 wherein said cam surface is formed in said wobble drive shaft.33. A drive apparatus for a reciprocating tool, comprising; a housing; arotatable drive shaft assembly located in said housing; an elongatedspindle located in said housing for reciprocating motion in itslengthwise direction, said spindle having a front end portion forattaching a cutting blade thereto and a rear portion; a front bushing insaid housing for supporting the front end portion of said spindle, saidbushing permitting reciprocating and limited angular motion of saidspindle therein; and a wobble drive mechanism comprising a wobble driveshaft connected to said drive shaft assembly, an elongated arm having alengthwise axis extending upwardly from said wobble drive shaft andincluding an upper pivot connection to said spindle for reciprocatingsaid spindle generally in its lengthwise direction during alternatingcutting and return strokes, said upper pivot connection preventingtranslational movement of said spindle relative to said arm in thedirection of said arm lengthwise axis; an elongated rocker having anupper end portion with an interface to said spindle, a lower end portionhaving two spaced apart side walls, each side wall having acounterweight pivot connection for connection to a counterweight, and ahousing pivot connection to said housing located between said upper andlower end portions; and a counterweight having a main portion thatextends above and on opposite sides of said spindle, side portions thatextend downwardly to said counterweight pivot connections, and a forwardextension from a bottom of each of said side portions, saidcounterweight pivot connections being connected to said forwardextensions; a support configuration associated with said counterweightand housing for supporting said counterweight while permittingreciprocating movement of said counterweight in said housing in adirection generally parallel to said spindle movement, said supportconfiguration comprising an elongated recess in each of said sideportions oriented in a direction generally parallel to said spindlemovement, and a pin mounted in said housing and operatively extending toeach of said recesses and permitting said reciprocating movement; and acam surface on said wobble drive shaft configured to move said pin andsaid counterweight in a vertical direction during reciprocation of saidcounterweight, said opposite ends of said pin being mounted in saidhousing in a manner permitting vertical movement thereof responsive torotation of said wobble drive shaft and cam for creating an arcingmotion to said counterweight for neutralizing arcing movement of saidspindle.
 34. A drive apparatus for a reciprocating tool, comprising; ahousing; a rotatable drive shaft assembly located in said housing; anelongated spindle having a lengthwise axis located in said housing forreciprocating motion, said spindle having a front end portion forattaching a cutting blade thereto and a rear portion with an outwardlycurved outer surface; a front bushing in said housing for supporting thefront end portion of said spindle; a wobble drive mechanism comprising awobble drive shaft connected to said drive shaft assembly, an elongatedarm having a lengthwise axis extending upwardly from said wobble driveshaft and including an upper interface for reciprocating said spindlegenerally in its lengthwise direction during alternating cutting andreturn strokes, said upper interface connecting said arm to said spindlein a manner that permits translational movement of said spindle relativeto said arm in the direction of the arm lengthwise axis; and a backbushing operatively connected to said housing and comprising acylindrical chamber configured to receive said outwardly curved outersurface of said rear portion of said spindle in close slidingengagement, the rear end portion of said back bushing being pivotablyconnected to said housing to permit pivoting movement of said bushingthereby providing orbital movement of said spindle during reciprocatingmotion thereof; a cam mechanism operatively associated with said driveshaft assembly configured to pivot said back bushing duringreciprocating motion of said spindle; an on/off lever mechanism forselectively permitting pivoting movement of said back bushing whenplaced in an on position and preventing pivoting movement of saidbushing when placed in an off position.